Transport In Cells

• What is the definition of diffusion?


  'The spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration.'
• Why does diffusion occur more frequently when particles are close together?


  Because they collide with each other more often, resulting in movement.
• Is diffusion an active or passive process?


  It is passive as no energy is required.
• What types of molecules can move across cell membranes via diffusion?


  Small molecules such as oxygen, glucose, amino acids, and water.
• Why can't starch and proteins cross the cell membrane?


  Because they are too big.
• How does oxygen diffuse in the lungs?

  Oxygen diffuses through the membranes of alveoli into red blood cells.
• What happens to red blood cells rich in oxygen?


  They are pumped around the body to cells that are low in oxygen.
• What is gas exchange?


  It is the movement of gases, such as oxygen and carbon dioxide, between the blood and the air.
• What waste product moves by diffusion from liver cells into the blood plasma?


  Urea.
• What is osmosis?


  The movement of water from a less concentrated solution to a more concentrated one through a partially permeable membrane.
• Why is osmosis considered a passive process?


  Because it does not use energy.
• What happens when a cell is placed in a dilute solution?


  Water will move into the cell.
• What is the effect of an isotonic solution on a cell?


  There will be no movement of water into or out of the cell.
• What occurs in a hypertonic solution?


  Water moves out of the cell.
• What happens to animal cells in a dilute external solution?


  Water will move into the cells causing them to burst.
• What is turgor in plant cells?


  It is the pressure caused by water moving into the vacuole, keeping the plant rigid.
• What is plasmolysis in plant cells?


  It is when the cell membrane moves away from the cell wall due to water loss.
• What is active transport?


  The movement of particles from an area of lower concentration to an area of higher concentration, against their concentration gradient.
• Why is active transport not considered passive?


  Because it requires energy from respiration.
• How do root hairs take up mineral ions?


  Through active transport from the soil into the cells.
• Why is active transport necessary in the small intestine?


  To move glucose and amino acids from the gut into the blood against their concentration gradient.
• What are the three common features of exchange organs that enhance their efficiency?


  1. Large Surface Area: Increases the area for exchange.
  2. Thin Membrane: Reduces diffusion distance.
  3. Good Blood Supply: Maintains concentration gradients.
• What are examples of exchange organs in organisms?


  • Plant leaves (for gas exchange during photosynthesis)
  • Fish gills (for oxygen uptake and carbon dioxide removal)